Overview of Aerobic Cellular Respiration

Oct 16, 2024

Cellular Respiration: Aerobic Respiration

Overview

  • Focus on the next stage of cellular respiration in the presence of oxygen (aerobic respiration).
  • Aerobic refers to the presence of oxygen.
  • Pyruvate molecules from glycolysis are further processed.

Pyruvate Oxidation

  • Process:

    • Carboxy group removed from pyruvate, facilitating its movement into the mitochondria.
    • Carboxy group forms CO2.
    • Exergonic reaction: Energy is used to reduce NAD+ to NADH.
    • Remaining structure forms acetyl group, binds with Coenzyme A to form Acetyl CoA.

  • Results:

    • 2 CO2, 2 Acetyl CoA, 2 NADH from two pyruvate molecules.

Citric Acid Cycle (Krebs Cycle)

  • Initiated by Acetyl CoA.

  • Acetyl group binds with oxaloacetate to form citrate (6 carbon molecule).

  • Steps:

    1. Citrate (6C) forms an intermediate, then oxidized to a 5C molecule, releasing CO2 and reducing NAD+ to NADH.
    2. 5C molecule oxidized to 4C molecule, releasing CO2 and reducing NAD+ to NADH.
    3. Exergonic step fuels conversion of GDP to GTP (substrate-level phosphorylation).
    4. 4C molecule oxidized, reducing FAD to FADH2.
    5. Further oxidation regenerates oxaloacetate, reducing NAD+ to NADH.

  • Outcomes per Glucose (2 cycles):

    • 2 GTP, 6 NADH, 2 FADH2, 4 CO2.

Oxidative Phosphorylation

  • Electron Transport:

    • Involves electron transport chain (ETC) in the inner mitochondrial membrane.
    • NADH and FADH2 are oxidized, donating electrons to the ETC.
    • Energy from electrons pumps hydrogen ions into the intermembrane space, creating a gradient.

  • Role of Oxygen:

    • Oxygen is the final electron acceptor, forming water when reduced.

  • Chemiosmosis:

    • Hydrogen ions flow back through ATP synthase, driving ATP production from ADP.

Summary of ATP Yield

  • Glycolysis: 2 ATP (substrate-level), 2 NADH.

  • Pyruvate Oxidation: 2 NADH, 2 CO2.

  • Citric Acid Cycle: 2 ATP, 6 NADH, 2 FADH2, 4 CO2.

  • Oxidative Phosphorylation: 26-28 ATP, 6 water (Oxygen as final acceptor).

  • Total Output per Glucose:

    • 30-32 ATP, 10 NADH, 2 FADH2, 6 CO2.

Next Steps

  • Discussion on cellular respiration without oxygen.
  • Regulation of cellular respiration for efficiency.

These notes cover the essential aspects of aerobic respiration, highlighting the roles of various molecules and processes in energy production.